1. Technical Field
The present invention relates to an organic electroluminescence element and a display device.
2. Related Art
Organic electroluminescence elements are promising for a wide range of applications because they are self-luminescent fully solid-state elements with high visibility and resistance to impact. Currently, although those using inorganic fluorescent materials are predominant and widely used, they have problems in that the running cost is high since an alternating voltage of 200 V or more at 50 Hz to 1000 Hz is necessary for operation, and in that the brightness is insufficient. On the other hand, organic electroluminescence element research using organic compounds was initiated by using single crystals of anthracene and the like at first, but the film thickness was as thick as approximately 1 mm, and a driving voltage of 100 V or more was required.
The luminescence of these elements is a phenomenon in which an electron is injected from one electrode and a hole is injected from the other electrode, whereby a fluorescent material in the element is excited to a high energy level, and the excited fluorescent material returns to the ground state through emission of excessive energy as light.
These electroluminescence elements having a layered structure has a structure in which an organic fluorescent material and a charge transporting organic matter (charge transporting material) are layered on an electrode, and holes and electrons are transferred in the charge transporting material and recombine with each other to emit light. Organic fluorescent material to be used include 8-quinolinol aluminum complexes and fluorescence-emitting organic dyes such as coumarin compounds. Examples of the charge transporting material include diamino compounds such as N,N-di(m-tolyl)N,N′-diphenylbenzidine and 1,1-bis[N,N-di(p-tolyl)aminophenyl]cyclohexane, and 4-(N,N-diphenyl)aminobenzaldehyde-N,N-diphenylhydrazone compounds.